What are the critical requirements to be considered for the security measures in Internet of Things (IoT) services? Further, how should those security resources be allocated? To provide valuable insight into these questions, this paper introduces a security assessment framework for the IoT service environment from an architectural perspective. Our proposed framework integrates fuzzy DEMATEL and fuzzy ANP to reflect dependence and feedback interrelations among security criteria and, ultimately, to weigh and prioritize them. The results, gleaned from the judgments of 38 security experts, revealed that security design should put more importance on the service layer, especially to ensure availability and trust. We believe that these results will contribute to the provision of more secure and reliable IoT services.Keywords Internet of Things · Security requirement · Security assessment · Fuzzy set theory The information age, created by the rapid advancement of information and communications technology (ICT) and the widespread adoption of wireless technologies, has presented an exciting new capability for both humans and diverse applications to extend the interconnectivity through the new dimension of "things" communication and integration [21]. Cisco predicts that by 2020, 50 billion things will be connected to the Internet via Internet of Things (IoT) technologies, generating revenues in excess of $19 trillion for industries worldwide [32].